The Extended Entity-Relationship Model is a more complex and high-level model that extends an E-R diagram to include more types of abstraction, and to more clearly express constraints. All of the concepts contained within an E-R diagram are included in the E-R model, along with additional concepts that cover more semantic information.
These additional concepts include:- generalization/specialization, union, inheritance, and subclass/super class.

 Relation: A relation is a table with columns and rows

 Attribute: An attribute is a named column of a relation.

 Domain: A domain is the set of allowable values for one or more attributes.

 Primary key: the candidate key that is selected to identify tuples uniquely within the relation.

 Foreign key: an attribute, or set of attributes, within one relation that matches the candidate key of some (possibly the same) relation.

 Integrity constraints:

Domain integrity: Describes the restriction on the set of allowed values for an attribute.

Entity Integrity: No attribute of a primary key can be null.

Referential Integrity: If a foreign key exists in a relation, either the foreign key value must match a candidate key value of some tuple in its home relation or the foreign key value must be wholly null.

Referential integrity is a relational database concept, which states that table relationships must always be consistent. In other words, any foreign key field must agree with the primary key that is referenced by the foreign key.

Views: The dynamic result of one or more relational operations operating on the base relations to produce another relation. A view is a virtual relation that does not necessarily exist in the Database but can be produced upon request by a particular user, at the time of request.

Null represents a value for an attribute that is currently unknown or is not applicable for this tuple.